Bing Webmaster blog suggests that placing keywords in the following areas on a web page will have the the greatest impact:
Page title (inside the <title> tags)
Body text headers (as used within tags such as <h1> </h1>, <h2> </h2>, and so on)
Links to other pages (the link text between the <a> </a> tags)
Meta tags (specifically when used with the name="description" and the name="keyword" parameters)
If rewriting some passages of text so that you can use more of your keywords in a natural sounding form in strategic areas of your pages is doable, then it is usually worthwhile to do so.
Lastly, don’t mistakenly think using keywords in body text is a waste of time. Your body text content is indexed just like everything else, and in the effort to determine the site’s theme and the relevance of your content to keywords, your body text is definitely considered within that process. Including your keywords and key phrases in your body text simply reinforces your use of those terms used in the higher priority parts of the page. But without their use in those aforementioned areas, they won’t stand out as easily as definitive keywords for your site’s pages.